The present invention relates to an electron beam exposure method and apparatus and, more particularly, to an electron beam exposure method and apparatus which can overwrite a pattern on an already written pattern with high precision, and a device manufacturing method using the same.
In an electron beam exposure apparatus, the position stability of an electron beam is an important factor that determines its work precision. As factors that impair the position stability of an electron beam, charging of a contaminant such as a carbon compound that has become attached inside an electron optical system for imaging an electron beam, or an electron beam position variation arising from a thermal or mechanical deformation of a structure for supporting the electron optical system or a sample base are known. When the electron beam position has varied, the relationship between the writing coordinate position defined by the electron beam and the coordinate position defined by a pattern already written on a sample deviates before or after writing, or during writing, thus impairing the overwriting precision.
Conventionally, a variation of the writing coordinate position defined by the electron beam due to an electron beam position variation is corrected by the following method.
A reference mark is formed on a movable stage which carries a sample such as a wafer or the like. The stage is then moved on the basis of a coordinate system defined by the stage to locate a standard mark at the design standard irradiation position of an electron beam, and a mark coordinate position (X0, Y0) of the reference mark is obtained by the electron beam. Writing is temporarily stopped during writing, and the stage is moved again to locate the reference mark at the standard irradiation position of the electron beam. The coordinate position of the standard position is detected by the electron beam to obtain a mark coordinate position (X1, Y1) at that time. Any difference (xcex94X1, xcex94Y1) between the previous mark coordinate position (X0, Y0) and the current mark coordinate position (X1, Y1) is calculated to obtain the electron beam position variation. Then, the deflection position of the electron beam or stage position is corrected based on this difference (xcex94X1, xcex94Y1). The aforementioned operation is repeated until the end of writing.
However, upon correcting such electron beam position variation in the conventional method, if the number of reference marks is one, since stage movement from the wafer writing area to the reference mark is required, writing must be stopped for several tens of seconds. When a plurality of reference marks is formed on the stage or wafer, the stage movement time can be shortened. However, the positions of all these reference marks must be measured prior to writing, resulting an increase in measurement time. As a result, in either case, the throughput of the electron beam exposure apparatus lowers.
It is an object of the present invention to provide an excellent electron beam exposure method and apparatus, which can solve the aforementioned problems, and a device manufacturing method.
It is another object of the present invention to attain efficient exposure by determining the regularity of the pattern layout on a substrate using some of a plurality of reference marks (a predetermined number of reference marks), and controlling exposure based on the regularity.
It is still another object of the present invention to attain position correction during exposure writing using at least one of the predetermined number reference marks used in determination of the regularity.
It is still another object of the present invention to attain position correction during exposure writing using a reference mark or marks which is or are not used in determination of the regularity.
In order to achieve the above objects, according one aspect of the present invention, an electron beam exposure method, which applies a photosensitive material to a substrate, on which a plurality of patterns and alignment marks associated with the plurality of patterns are formed to regularly line up along a design layout coordinate system, and overwrites a pattern on the respective patterns by moving a stage that carries the substrate relative to an electron beam, comprises: the first detection step of selecting some of the plurality of alignment marks, and sequentially detecting the positions of the selected alignment marks; the step of determining regularity of a layout of the plurality of patterns on the substrate on the basis of design coordinate values and actually measured values of the alignment marks in the first detection step; the step of writing a pattern on the respective patterns by moving the stage relative to the electron beam on the basis of the regularity of the layout of the plurality of patterns; the second detection step of detecting positions of the selected alignment marks by irradiating the selected alignment marks with the electron beam and detecting electrons reflected by the alignment marks; and the step of calculating the difference between actually measured values of the alignment marks in the second detection step, and the actually measured values of the alignment marks in the first detection step, and correcting a relative position between the electron beam and stage on the basis of the difference.
According to another aspect of the present invention, an electron beam exposure method, which applies a photosensitive material to a substrate, on which a plurality of patterns and alignment marks associated with the plurality of patterns are formed to regularly line up along a design layout coordinate system, and overwrites a pattern on the respective patterns by moving a stage that carries the substrate relative to an electron beam, comprises: the first detection step of selecting some of the plurality of alignment marks, and sequentially detecting the positions of the selected alignment marks; the step of determining regularity of a layout of the plurality of patterns on the substrate on the basis of design coordinate values and actually measured values of the alignment marks in the first detection step; the step of writing a pattern on the respective patterns by moving the stage relative to the electron beam on the basis of the regularity of the layout of the plurality of patterns; the second detection step of detecting positions of the selected alignment marks by irradiating the alignment marks with the electron beam and detecting electrons reflected by the alignment marks; and the step of calculating the difference between actually measured values of the alignment marks in the second detection step, and coordinate values of the alignment marks which are calculated from the regularity of the layout, and correcting a relative position between the electron beam and stage on the basis of the difference.
According to still another aspect of the present invention, there is provided an electron beam exposure apparatus, which applies a photosensitive material to a substrate, on which a plurality of patterns and alignment marks associated with the plurality of patterns are formed to regularly line up along a design layout coordinate system, and overwrites a pattern on the respective patterns by an electron beam, comprising: deflection means for deflecting the electron beam on the substrate; a stage which moves while carrying the substrate; a distance measurement system for detecting a position of the stage; a first detection system for detecting a position relative to an object to be detected on the stage, and detecting the position of the object to be detected in cooperation with the distance measurement system; a second detection system for irradiating the object to be irradiated with the electron beam on the stage with the electron beam, detecting electrons reflected by the object to be irradiated, and detecting the position of the object to be irradiated in cooperation with the distance measurement system; and control means for selecting some of the plurality of alignment marks, making the first detection system sequentially detect positions of the selected alignment marks, determining regularity of a layout of the plurality of patterns on the substrate on the basis of design coordinate values and actually measured values of the alignment marks by the first detection system, writing a pattern on the respective patterns by moving the substrate relative to the electron beam using the deflection means and stage on the basis of the regularity of the layout of the plurality of patterns, making the second detection system detect positions of the selected alignment marks during writing of the pattern on the substrate, calculating a difference between actually measured values of the selected alignment marks of the first and second detection systems, and correcting a relative position between the electron beam and the substrate using at least one of the deflection means and the stage on the basis of the calculated difference.
According to still another aspect of the present invention, there is provided an electron beam exposure apparatus, which applies a photosensitive material to a substrate, on which a plurality of patterns and alignment marks associated with the plurality of patterns are formed to regularly line up along a design layout coordinate system, and overwrites a pattern on the respective patterns by an electron beam, comprising: deflection means for deflecting the electron beam on the substrate; a stage which moves while carrying the substrate; a distance measurement system for detecting a position of the stage; a first detection system for detecting a position relative to an object to be detected on the stage, and detecting the position of the object to be detected in cooperation with the distance measurement system; a second detection system for irradiating the object to be irradiated with the electron beam on the stage with the electron beam, detecting electrons reflected by the object to be irradiated, and detecting the position of the object to be irradiated in cooperation with the distance measurement system; and control means for selecting some of the plurality of alignment marks, making the first detection system sequentially detect positions of the elected alignment marks, determining regularity of a layout of the plurality of patterns oh the substrate on the basis of design coordinate values and actually measured values of the alignment marks by the first detection system, writing a pattern on the respective patterns by moving the substrate relative to the electron beam using the deflection means and stage on the basis of the regularity of the layout of the plurality of patterns, making the second detection system detect positions of the selected alignment marks during writing of the pattern on the substrate, calculating a difference between actually measured values of the selected alignment marks and coordinate values of the selected alignment marks which are calculated based on the regularity of the layout, and correcting a relative position between the electron beam and the substrate using at least one of the deflection means and the stage on the basis of the calculated difference.
Furthermore, according to still another aspect of the present invention, there is provided a device manufacturing method that manufactures a device by manufacturing processes including one of the aforementioned electron beam exposure methods.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.